Figure 5.

ROS-mediated apoptosis in proton beam-irradiated HepG2 cells. (A) Level of ROS in LLC and HepG2 cells measured by DCFDA. ^*P < 0.01 versus control in each cell line (no treatment of proton). (B) When NAC (5 mM) was treated 4 h before proton irradiation, the cell death induced by proton beam (100 Gy) was restored both in LLC and HepG2 cells. ^*P < 0.01 versus only proton treated one in each cell line. (C) Caspase-3 activities were measured and compared with control non-treated cells after the irradiation of proton beam (100 Gy) in LLC and HepG2 cells. ^*P < 0.01 between control and only proton treated one in each cell line. ^**P < 0.01 between only proton treated and NAC pretreated one in each cell line. (D) HepG2 cells were treated with proton beam 100 Gy and for the detection of phosphorylation of MAPKs and Akt, cells were collected at 1 h after irradiation and the kinase levels were detected by Western analysis. (E) HepG2 cells were transfected with DN-p38 MAPK or DN-JNK and on next day irradiated with proton beam (10 or 50 Gy). After 24 h, cell viability was determined with MTT assay. (A-C, E) All data were shown as a fold induction of control cell viability. The data were Mean ± SD (n = 5). All experiments were performed in duplicate. ^*P < 0.01 versus control in each DN transfectant.